|Publication number||US6853474 B2|
|Application number||US 10/117,554|
|Publication date||8 Feb 2005|
|Filing date||4 Apr 2002|
|Priority date||4 Apr 2002|
|Also published as||US20030189025|
|Publication number||10117554, 117554, US 6853474 B2, US 6853474B2, US-B2-6853474, US6853474 B2, US6853474B2|
|Inventors||Chris C. Yu, Vlasta Brusic|
|Original Assignee||Cabot Microelectronics Corporation|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (21), Non-Patent Citations (1), Referenced by (1), Classifications (8), Legal Events (4)|
|External Links: USPTO, USPTO Assignment, Espacenet|
The present invention relates to the field of optical switches. More specifically, the present invention relates to the manufacture of micro-acousto-optic modulators, which may be used as optical switches as well as optical switches manufactured by the methods of this invention.
Currently, network and other telecommunications industries are utilizing optic signals of visible and invisible light wavelengths traveling down optical fibers to transfer information from one location with another. However, the switches currently used to redirect information down these optical pathways utilize electric signals instead of optic signal. Therefore, the optic signal from the optical fiber must be converted into an electric signal in order to pass through a switch and then reconverted into a optic signal before continuing its travel down another optical fiber. This switching process severely slows the travel time of information within a fiber optic network and increases the cost of transmitting that information. Therefore, as network and other telecommunications infrastructures rely more heavily upon optical fibers and optical-based technologies, the development and use of optical switches become increasingly important.
As discussed in D. J. Bishop et al., The Rise of Optical Switching, Scientific American, vol. 284(1), pp. 88-94 (2001), several approaches to optical switches are currently being investigated. Among these approaches, there are Micro-Electro-Mechanical Systems (MEMS), waveguide circuits, acousto-optical modulation, “micro-bubble” switches, and liquid crystal based switches. One key performance requirement for an optical switch is its ability to handle an increased number of input-to-output channels for meeting current and future bandwidth demand.
One way to meet this requirement is to increase optical switch density via reduction in optical switch size. While there are many ideas and options for optical switches, there have been few technologies that are able to meet the requirement of reduction in switch size along with demonstrated performance excellence, manufacturing robustness and operation reliability. Many of the existing optical switches are manufactured as discrete components. These components tend to be relatively large in size, expensive (due to extensive manual operations required), and manufactured at a lower yield. For example, acousto-optic modulator type switches, have a typical minimum component size of ˜3 mm. Other approaches, such as MEMS, involve moving parts, which not only limit switching speed, but also raise concerns over reliability and lifetime of such device.
Therefore, there exists a need for optical switches that are small, robust, reliable, and that are simple to manufacture.
The present invention relates to a process for fabricating micro-acousto-optic modulators comprising etching a first set of trenches into a substrate having an exposed top surface; depositing a transducer material onto the exposed substrate surface and into the first set of trenches to form at least one transducer; removing the transducer material from the surface of the substrate; etching a second set of trenches into the substrate and adjacent to the transducer material, such that the transducer is sandwiched between two trenches; depositing an electrode material onto the exposed substrate surface and into the second set of trenches to form at least two electrodes; and removing electrode material from the surface of the substrate.
The present invention also relates to a process for fabricating micro-acousto-optic modulators, comprising forming a substrate having an exposed top surface; depositing a first layer of electrode material onto the surface of the substrate; depositing a layer of transducer material onto the first layer of electrode material; patterning the substrate, the first layer of electrode material and the transducer material to form a first plurality of features, each having a top surface, and to form gaps between the features; depositing a first material layer on top of the first plurality of features and into the gaps; polishing the first material layer to form a co-planer surface comprising the transducer material layer and the first material, wherein the first material layer remains in the gaps; depositing a second layer of electrode material onto the co-planar surface; patterning the second electrode material layer and the transducer material layer to form a second plurality of features, each having a top surface, and to form gaps between the second plurality of features, wherein a portion of the first electrode layer is exposed in the gaps; depositing a second material layer on top of the second plurality of features and into the gaps; patterning the second material layer to form at least one pair of interconnection trenches, wherein one interconnection trench exposes a portion of the first electrode material layer and the other trench exposes a portion of the second electrode material layer; depositing a third layer of electrode material onto the surface of the second material layer and into the interconnection trenches; patterning the third layer of electrode material to form pads of electrode material, wherein each pad is connected to only one interconnection trench containing third electrode material.
The present invention also relates to a micro-acousto-optic modulator comprising a substrate having at least one inlay comprising a first layer of electrode material, a layer of transducer material, and a second layer of electrode material, wherein the layer of transducer material is located between the first layer of electrode material and the second layer of electrode material.
The present invention further relates to a micro-acousto-optic modulator comprising a substrate having an exposed surface, a first layer of electrode material attached to the surface of the substrate, a layer of transducer material attached to the first layer of electrode material, and a second layer of electrode material attached to the layer of transducer material.
In the present invention, a microelectronics process technology is utilized to manufacture micro acousto-optic modulators for optical switching. With this process, reduction in acousto-optic modulator size by a factor of up to 1000 can be achieved. In addition, because the resulting acousto-optic modulator does not involve moving parts, high speed, good reliability, and long lifetime are achievable.
The processes of the present invention use many standard and well known microelectronics fabrication techniques including, but not limited to, lithography, dry etch techniques, wet etch techniques, demascene, chemical vapor deposition (CVD) and/or physical vapor deposition (PVD), and chemical mechanical polishing (CMP), to manufacture micro-acousto-optic modulators 10. As shown in
The choice of polishing composition or slurry is an important factor in the CMP step. Depending on the choice of ingredients such as oxidizing agents, film forming agents, acids, bases, surfactants, complexing agents, abrasives, and other useful additives, the polishing slurry can be tailored to provide effective polishing of the substrate layer(s) at desired polishing rates while minimizing surface imperfections, defects and corrosion and erosion. Furthermore, the polishing composition may be selected to provide controlled polishing selectivities to other thin-film materials used in substrate manufacturing. In the present invention, a polishing composition with a high polishing selectivity towards the transducer material in comparison to substrate material is preferred. Most preferably, a polishing composition with a selectivity of greater than 5:1 is used.
Examples of CMP polishing compositions and slurries are disclosed, in U.S. Pat. Nos. 6,068,787, 6,063,306, 6,033,596, 6,039,891, 6,015,506, 5,954,997, 5,993,686, 5,783,489, 5,244,523, 5,209,816, 5,340,370, 4,789,648, 5,391,258, 5,476,606, 5,527,423, 5,354,490, 5,157,876, 5,137,544, 4,956,313, the specifications of each of which are incorporated herein by reference.
In order to apply AC voltage 30 to transducer material 25, transducer material 25 must be positioned between two electrodes 20. Therefore, a second set of trenches 19′ is etched into substrate 15 along both sides of each layer of transducer material 25, in
After creating the second set of trenches 19′, an electrode material 20 is deposited onto the surface of substrate 15 in an amount sufficient to fill the second set of trenches 19′, as shown in
It is possible, when silica is used for substrate 15, that electrode material 20 may not adhere well to substrate 15. Therefore, as an optional step, an adhesion layer such as a layer of Ti, TiN, TiW, alloys thereof or mixtures thereof can be deposited in second set of trenches 19′ prior to the deposition of electrode material 20 in order to enhance the adhesion of electrode material 20.
Finally, as shown in
If the desired transducer 25 or electrode 20 materials are not easily polished using chemical mechanical polishing techniques, an alternative embodiment of the disclosed process may be used. In this alternative process, shown in
Next, as shown in
Next, as shown in
Next, as shown in
After acousto-optic modulator 10 has been fabricated according to the present invention, further processing will be necessary to complete the optical switch. For example, further processing may include (1) processes to interconnect the two electrodes to a voltage source, (2) processes to optically connect, typically via optical waveguides, the acousto-optic modulators to the optical signals to be processed, and (3) final assembly of the products containing the modulators.
The present invention discloses a micro-acousto-optic modulator based optical switch and a process for fabricating the switch using the microelectronics manufacturing technology. A significant reduction in optical switch feature size can be achieved through the present invention. The disclosed micro-acousto-optic modulator is highly integrated, which allows the resulting optical switch to exhibit improved throughput and higher density, functionality, and yield at a lower cost due to the reduction in mechanical parts and manufacturing cost, due to reduction in labor cost.
It should be understood that a wide range of changes and modifications can be made to the embodiments of process flow and acousto-optic modulators described above. For instance, the basic process disclosed in the present invention can be applied to the manufacture of other types of optical switches, such as liquid crystal based optical switches. It is therefore intended that the foregoing description illustrates rather than limits this invention, and that it is the following claims, including all equivalents, which define this invention.
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|1||Bishop, et al., "The Rise of Optical Switching", Scientific American, ISSN 0036-8733 Munn & Company, Jan. 2001, vol. 284(1), pp. 88-94.|
|Citing Patent||Filing date||Publication date||Applicant||Title|
|US8873131||26 Jun 2012||28 Oct 2014||Samsung Electronics Co., Ltd.||Acousto-optic device having multi-layer nanostructure, optical scanner, optical modulator, and display apparatus using the acousto-optic device|
|U.S. Classification||359/285, 359/305|
|International Classification||G02F1/33, G02F1/11|
|Cooperative Classification||G02F1/33, G02F1/11|
|European Classification||G02F1/11, G02F1/33|
|15 May 2002||AS||Assignment|
Owner name: CABOT MICROELECTRONICS CORPORATION, ILLINOIS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:YU, CHRIS C.;BRUSIC, VLASTA;REEL/FRAME:012697/0731;SIGNING DATES FROM 20020317 TO 20020319
|6 Jun 2008||FPAY||Fee payment|
Year of fee payment: 4
|16 Feb 2012||AS||Assignment|
Owner name: BANK OF AMERICA, N.A., AS ADMINISTRATIVE AGENT, IL
Free format text: NOTICE OF SECURITY INTEREST IN PATENTS;ASSIGNOR:CABOT MICROELECTRONICS CORPORATION;REEL/FRAME:027727/0275
Effective date: 20120213
|17 Jul 2012||FPAY||Fee payment|
Year of fee payment: 8